Functional differences and regulation of gene expression of phosphoribosylpyrophophate synthetase isozymes

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1. Cloning of CDNA coding rat phosphoribosylpyrophosphate synthetase revealed two distinct types of subunit, referred to as PRS I and PRS II. Tissue-specific expression of PRS I and PRS II genes was shown. In the testis, an additional transcript was noted.2. The chromosomal localization of human PRS I and PRS II genes was determined. In addition, two PRPS1 (PRS I gene)-related genes (PRPS1L1 and PRPS1L2) were found.3. Complete cDNA sequence of rat PRS I and PRS II were determined.4. Genomic DNA corresponding to rat PRPS1 was cloned and characterized. The gene consisted of seven exons.5. cDNA for testis-specific human phosphoribosylpyrophosphate synthetase was cloned and characterized. The gene was located at chromosome 7. The mRNA had a non-AUG initiation codon, ACG.6. cDNAs for rat PRS I and PRS II were inserted into the vector and expressed in Escherichia coli. The enzyme activities of E. coli cells transformed with the expression vectors were 10-20 fold greater than that of untransformed E. coli cells.